The present invention relates to illumenation fiber optic conduits, and fiber optic configurations or assemblies composed of fiber optics, channels and/or jacketing(s) adapted to render them fire retardant and/or self-extinguishing. The conduits can be large core plastic optical fiber linear and end light emitting, or side light emitting conduits.
Fiber optic conduits are well-known for illumination applications and have been described in numerous publications. Methods of preparation and use have also been extensively disclosed in these publications, such as U.S. Pat. Nos. 5,298,327 and 5,067,831.
Most illumination fiber optics are made from thermoplastic or thermoset polymeric materials and mostly are cladded by fluoropolymers. In some instances, clear jacketings are also extruded onto a single or multiple fiber optics to afford resistance against environmental and or mechanical damage or to enhance the optical appearance. In another instance, the fiber optics are configured by cutting or notching, among other methods to emit the light radially at a predetermined e.g., 45 degree angle relative to the longitudinal axis of the optic. Also, a polymeric channel may be utilized as a reflector or as a component to affix the orientation of the cuts in such side (linear light) emitting optics and, consequently to affix orientation of the emitted light. Because of the polymeric nature of the components included in the assemblies, these light forms are susceptible to fire, and burn easily and may thereby contribute to progression of fire in areas such as buildings, marine vessels, ground and air transportation vessels and the like in their unmodified form. In some applications, the end light emitting optics have been encased in metal conduits that are similar to conduits utilized in electric wiring applications. Such an arrangement prohibitively increases the cost of the application, both in terms of materials and labor. In the side emitting configurations, this type of conduit can not be used, because the pathway for light emission is blocked. The disadvantages disclosed above limit the applications for construction, transportation, signs, emergency vehicles, and traffic management among others.
The present invention is directed to large core plastic optical fibers (LCPOF), as that term has become known in the industry, which are modified to provide a fire retardancy or fire extinshing capability. LCPOF is distinguished from fiber optic conduits used in the communication field principally in terms of the size, i.e., outer diameter of the core, as well as the core material composition. The core is the component of the fiber optic which actively transmits the electromagnetic radiation. Also, LCPOF is distinguished from communications type fiber optics in that it is generally limited to transmission of radiation in the visible light spectrum, i.e., in the range of about 360-800 xcexcm. Hence, LCPOF is usual for end-lit or side-lit illumination applications. Typically an LCPOF is a fiber optic which includes a core having a minimum diameter of approximately 3.0 millimeters. LCPOF ranges in size from a diameter of about 3.0 millimeters up to and including about 25 millimeters (about 1.0 inch) for most applications.
In many applications, light transmitting fiber optic conduits and/or assemblies must meet or exceed specific fire, smoke and toxicity standards imposed by various civilian governmental agencies, military services, independent testing laboratories and/or other regulatory agencies. For example, for the construction industry, the optics must comply with and/or pass the testing procedures of Underwriters Laboratory Standard 910. In military applications, the assembly must pass the Military Specification C 24643-A ( Mil Spec C 24643-A) Flame Test, or Underwriters Laboratory IEEE 383 1974. With respect to toxicity and smoke generation, the assembly must meet certain standards, such as Naval Engineering Standard 711 (NES 711 Smoke Index Test) and Naval Engineering Standard 713 (NES 713 Toxicity Index Test).
For end emitting assemblies, particularly for communication applications, some fire retardant arrangements are known, such as described in U.S. Pat. Nos. 5,173,960; 5,204,928; and 5,136,683. Nonetheless, such assemblies have been found not to be useful in LCPOF applications. Such assemblies, similarly, can not be utilized for side or linear emitting type applications.
The present invention relates to individual polymeric optical conduits and optical conduit assemblies that include fire retardants, polymeric fiber optic(s), channel(s) and/or jacketing(s) whereby flame retardancy is enhanced and the optic and/or assembly is made, preferably, self extinguishing. Preferred embodiments of the present invention also exhibit relatively low smoke generating properties and relatively low toxicity in order to meet governmental and industry standards.
Preferred embodiments of the present invention are directed to either side light emitting fiber optics and assemblies and/or LCPOF end emitting fiber optics and assemblies all of which include a polymeric thermoset core that is clad with a fluoropolymer cladding. The assemblies also include at least one jacket, and in some preferred embodiments two jackets, which encase the clad core as well as, in some instances a channel which partially surrounds the clad core. In accordance with the present invention, a fire retardant material, such as, for example, an intumescent material, is positioned outside of the clad core and either incorporated within one or both of the surrounding jackets, is incorporated into the channel material, or is otherwise positioned in a layer between the outermost jacket and the clad core. The fire retardant material is generally placed along the length of the clad core fiber optic and at least partially surrounds the radial periphery of the clad core, so that in case of a fire, the fire retardant material will function to retard the fire. In some preferred embodiments and under some conditions the material will function to extinguish the fire.
Within the scope of the present invention, the preferred fire retardant material used in the present invention is an intumescent material. For purposes of the present invention, the term intumescent is used in the sense as defined by Whittington""s Dictionary of Plastics, Third Edition (1993), published by Technomatic Publishing Company of Lancaster, Pa., at page 260 as: xe2x80x9cThe foaming and swelling of a plastic when exposed to high surface temperature of flames. It has particular reference to ablative urethane used on rocket nose cones, and to INTUMESCENT COATINGS, . . . xe2x80x9d.
In a first preferred embodiment of the invention, the polymeric thermoset light transmitting clad core is jacketed with a first polymeric jacket that includes intumescent material incorporated therein. The intumescent, jacketed clad core is surrounded by a second jacket, which is also made of a polymeric material, and which functions to contain the first jacket during a fire sufficient to cause jacket 1 to expand radially inwardly, rather than outwardly, and to form a char in the light transmitting clad core, thus hindering the propagation of the fire and, preferably, extinguishing the flame.
Alternatively, a second preferred embodiment comprises a polymeric thermoset light transmitting core, cladded with a fluoropolymer and subsequently jacketed with a polymeric jacket including an exuding type of fire retardant material (jacket 1) and further jacketed by a polymeric material (jacket 2) which has the property of containing jacket 1 sufficiently whereby, in the case of a fire, jacket 1 exudes a fire retarder such as water, onto the light transmitting clad-core, thus hindering the propagation of the fire and eventually extinguishing the flame. Specifically, with respect to the second preferred embodiment, in contrast to the first preferred embodiment in which the fire retardant material is an intumescent material, and expands during a fire, the fire retardant material used in the second preferred embodiment does not expand, but exudes. For example, in the second preferred embodiment, a material which contains compounds, that under fire conditions, will react to form a fire retardant or extinguishing material, such as water, in sufficient amounts is used.
Alternatively, a third preferred embodiment comprises a plurality of light transmitting cores, each cladded with a fluoropolymer, that are held in a bundle and with the bundle subsequently jacketed with a first polymeric jacket that includes intumescent materials and further jacketed by a second polymeric material which has the property of containing the first jacket sufficiently whereby, in the case of a fire, the first jacket expands, preferably inwardlyxe2x80x94rather than outwardlyxe2x80x94while forming a char onto the light transmitting clad-cores, thus hindering the propagation of the fire and eventually extinguishing the flame.
A fourth preferred embodiment of the present invention includes a polymeric thermoset light transmitting core, cladded with a fluoropolymer that is notched at predetermined intervals along its length. The notched, clad core is then placed and precisely oriented within a polymeric channel light that is emitted from the cuts and toward the channel and then reflected out of the optic at a predetermined angle. The channel and its associated clad core is then jacketed with a polymeric material that is, preferably, transparent or translucent, and which has the property of containing the channel and clad core sufficiently whereby, in the case of a fire, the channel expands inwardlyxe2x80x94rather than outwardlyxe2x80x94while forming a char onto the light transmitting clad-core, thus hindering the propagation of the fire and preferably, eventually extinguishing the flame.
In a fifth preferred embodiment, the present invention assembly includes a polymeric thermoset light transmitting core, cladded with a fluoropolymer, notched at predetermined intervals, and oriented within a polymeric channelxe2x80x94to emit light away from the cuts at a predetermined angle. The fifth embodiment is also contained within an outer conduit, and is the fourth embodiment. In this fifth embodiment the channel includes a non-intumescent, fire retardant material which has the property of containing the channel and clad-core sufficiently whereby, in the case of a fire, the channel exudes a fire retarder onto the light transmitting clad-core, thus hindering the propagation of the fire and eventually extinguishing the flame.
The illumination fiber optic assemblies of the present invention exhibit fire retardancy and/or self-extinguishing properties when exposed to fire. Also, the embodiments of the present invention, preferably, exhibit sufficiently low toxicity and low smoke to comply with appropriate federal (such as military), state, and local requirements, as well as to comply with various industry standards, such as set forth in various independent testing laboratory procedures. Illumination fiber optic assemblies exhibiting such fire, smoke and toxicity properties are believed to have been unknown prior to the present invention.